As functions of a mobile terminal such as a mobile phone become increasingly powerful, a user frequently uses the mobile terminal, resulting in greater power consumption and more frequent charging of the mobile terminal. Pursuit of a thin and light device makes a manufacturer choose a charging interface of increasingly small dimensions. As a result, distances between pins in the charging interface become smaller. In a case of ingress of water, iron filings, carbon powder, or the like into the device, the pins in the charging interface may be short-circuited, and consequently the device may be burned or deformed or even a fire accident may be caused during a process of charging the device.
To resolve the foregoing problem, an existing solution is as follows: A PTC (Positive Temperature Coefficient) resistor is added near the charging interface. When the charging interface generates heat and causes a high temperature, a temperature of the PTC resistor increases, bringing a rapid increase in resistance of the PTC resistor and preventing a large current from passing through, and ensuring overcurrent protection.
However, problems of the existing solution are as follows: The PTC resistor is a thermosensitive component. If a trigger temperature of the PTC resistor is set too low, an erroneous action may occur, and if the trigger temperature is set too high, the PTC resistor cannot provide good protection. In addition, when a temperature of the charging interface reaches the trigger temperature of the PTC resistor, there is a delay for a disconnecting action of the PTC resistor, which may damage the charging interface.